Vacuum tube



June 18, 1935. A. BRASCH ET AL VACUUM TUBE Filed Sept. 13, 1930 2Sheets-Sheet l ifig i.

VACUUM TUBE Filed Sept. 15, 1930 2 Sheets-Sheet 2 Patented June 18, 1935UNITED STATES PATENT OFFICE VACUUM TUBE Arno Brasch and Fritz Lange,Berlin, Germany 10 Claims.

The present invention relates to improvements in vacuum tubes andparticularly to vacuum tubes for generating very rapid corpuscular rays,both of a positive as well as a negative kind,

with a more specific object of creating very hard X-rays.

The arrangement described in the following furthermore enables thevoltage at the tube to be increased to such extent that a conversion ofelements may be performed by means of the corpuscular rays acceleratedtherein.

Generally speaking, it is impossible to operate a single-stage dischargetube with voltages much in excess of 200,000 volts, as rupture of thewalls will then take place.

We have ascertained by experiment that it is possible to operatesingle-stage discharge tubes with voltages much in excess of 1 millionvolts without employing an actual guard for the walls such as heretoforevariously proposed and also employed in practice.

In the course of our experiments we have discovered that the occurrenceof independent discharge is apparently initiated by a kind of slidingdischarge taking place along the inner wall of the tube. lamination ofthe total inner wall of the tube along the discharge passage by means ofmore or less conductive annular structures absolute freedom ofindependent discharge could be-observed even with the use of alternatecurrent of 50 periods and a voltage of 1,300,000 volts. A particularlyremarkable feature associated with the invention consists in the factthat particular claims of any kind do'not require to be placed on thequality of the vacuum-employed, so that for the construction of the tubeit is even possible to employ organic materials which, as well known,always possess a certain pressure.

By sufliciently fine divisioning or lamination of the discharge passage,operations may be performed even with the most extreme voltages with avacuum not exceeding more than 1/1000 mm. Hg. This fact is particularlyimportant in the generation of extremely rapid passage rays.

The annular laminations may .be applied in various different ways. Sinceit is important to make the slideway between the individual laminationsas large as possible, whereas on the other hand it is also desirable toprovide as many divisions as possible over a given space, thearrangement is preferably such that the portions of the insulating wallsituated between the individual laminations are formed to provide pro-By extremely fine divisioning orjections or grooves. The divisioning maythen be performed in these grooves which serve simultaneously formounting the annular laminations and to increase the insulation betweenthem.

In the particular arrangement employed for 5 the experiments the vacuumtube consisted of thick-walled porcelain (2 centimeters) 8 centi- Imeters in diameter, which was particularly safe against rupture. Thetotal length of the tube amounted toapproximately 2 meters. The lami- 10nations consisted of approximately200 metal rings fitted at equaldistances. apart. Since the rings consisted of a resilient metal(nickel) it was possible to dispense with any particular holding meansfor the same. Expulsion of the gas from 15 the various materialsemployed was also unnecessary. The electrode feed was performed by meansof metallic caps, which were cemented on. Inwardly projecting electrodeswere not employed, as these would have been detrimental to 20 the effectof the laminations.

The invention is shown byway of example in the accompanying drawings.

Figures 1 to 6 represent diagrammatically different constructional formsof the vacuum (118- 25 charge tube, Fig. l being a longitudinal section;Fig. 2 a fragmentary perspective cross section of Fig. 1; in Fig. 3--isshown a modification of Fig. 1 and Figs. 4, 5 and 6 are similar views toP18.

1 of still other modifications of the invention. 30

Referring to Figure 1, the tube is made of insulating material and isclosed by two metal end caps 2 and 3. The glow-cathode 4 extendssuitably insula'ted through the cap 3 while the watercooled anticathode5 is mounted on the cap I. 35 The subdivision or lamination of the innerwall of the tube I is effected, as shown in Figure 1, by closelyadjacent rings 8 of more or less conductive material. The position ofthe rings is shown diagrammatically in Figure 2.

The annular laminating structures or rings are closely spaced along thewalls, the spacing being such that, conforming with the correspondingdistribution of the potential, the difference in potential between anytwo neighboring rings will 5 be smaller than the minimum necessitated bythe vacuum and the form and material of the tube to initiate the slidingdischarge between rings.

In Figure 3, the sliding path is enlarged by suit- 50 able grooves I lbetween the rings. For this purpose, the inner lining of the tube l isgrooved or corrugated and the rings 6 are diagrammatically indicated assupported bythe projecting portions of the corrugations while thedischarge 55 tube I is closed by the caps 2 and 3 in the usual manner,these caps bearing the anti-cathode 5 and the cathode 4 respectively.

Figure 4 shows\a further constructional form wherein the means fordistributing the potential difference along the walls of the tube toprevent sliding discharges is in the form of a helix 9 inserted in thesmooth interior of the tube I so that a helix connection with greatinduction is formed for current impulses and alternating voltage. Thishelix corresponds to the laminations G in Figs. 1 to 3.

Fig. 5 shows a further constructional form wherein the envelopecomprises the internally corrugated tubular portion l' of insulatingmaterial and the end cap members 2' and 3'. The cathode,diagrammatically shown at l, is carried by the end cap 2', and the anodeor anticathode 5' is carried by the end cap 3'. The annular structuresdiagrammatically indicated at 6' for dividing the potential diiferencealong the walls of the tube are shown mounted in the grooves.

Fig. 6 shows a further constructional form in which the internallycorrugated tubular portion I of insulating material having thedivisioning means 6', is provided with one end cap 2 carrying a suitablecathode 4", and in whichthe means providing the anode 5" serves as thecap for the other end of the tubular insulating portion.

It the tubes are operated in a special insulating medium, for exampleoil, it will naturally be desirable to reduce the length as far ascompatible, in order to be able to pass high emissional outputs throughthe tube without obstruction. With suillciently small dimensioning ofthe laminations it is also possible to provide several hundredlaminations over a length of tube amounting to only between 30 and 40centimeters. Any emissional arrangement of the known kind may beemployed for generating passage or cathode rays. The experiments madehave shown that any desired voltage may be applied to a vacuum chamberup to the occurrence of the so-called Lilienfeld eifect (10 to 10"volt-cm), and that the voltage limitation hitherto observed atapproximately between 300,000 and 400,000 volts in connection withsingle-stage tubes is merely occasioned by certain sliding efiects alongthe inner wall without, as hitherto assumed, the quality of the vacuumconstituting a governing factor.

What we claim as new and desire to secure by Letters Patent is:

1. A vacuum discharge tube comprising an envelope,- a cathode and ananode mounted therein and spaced to form a relatively long dischargepaththerebetween for the desired discharge between cathode and anode, aplurality of closely spaced, electrically conductive rings within theenvelope, said rings extending along said entire discharge-path andbeing electrically insulated from each other and from the exterior ofsaid envelope.

2. A vacuum discharge tube comprising an envelope, a cathode and ananode mounted therein and spaced to form a discharge-path therebetweenfor the desired discharge between cathode and anode, a plurality ofclosely spaced electrically conductive rings within the envelope, saidrings extending along said discharge-path and being electricallyinsulated from the exterior of said envelope; said' envelope beinginternally corrugated to form seats for said conductive rings andincrease the insulation against sliding discharges between rings.

3. A vacuum discharge tube comprising an envelope, a cathode and ananode mounted therein and spaced to form a discharge-path therebetweenfor the desired discharge between cathode and anode, a plurality ofclosely spaced, electrically conductive rings within the envelope, saidrings extending along said discharge-path and being electricallyinsulated from the exterior oi said envelope; said envelope beinginternally corrugated to provide a large surface between each of twoneighboring conductive rings to insulate against the initiation ofsliding discharges.

4. A vacuum discharge tube for very high voltages having cathode andanti-cathode members, comprising an open ended tubular member orinsulating material, a plurality of conductive laminations uniformlyspaced within said tubular member, a cap secured on each end of thetubular member forming respectively seats for said cathode andanti-cathode members, said tubular member being provided with internalcorrugations having the same spacing as said laminations and the apicesof the corrugations iorming seats for the laminations.

5. A vacuum discharge tube comprising an envelope having a substantiallycylindrical insulating portion, electrodes mounted therein adjacent theends thereof and spaced to form a dischargepath, a plurality ofelectrically conductive loops within the envelope, said loops extendingalong said discharge-path and having an exterior diameter substantiallythe same as the interior diameter of said envelope and beingelectrically insulated from the exterior of said envelope; said loopsbeing interconnected.

6. A vacuum discharge tube comprising an envelope, an emissional cathodeand an anode mounted therein and spaced to form a relatively longdischarge-path therebetween for the desired discharge from the cathodeto the anode, a plurality of electrically conductive loop-like memberswithin the envelope, said loop-like members extending along said entiredischarge-path and having substantially the same exterior diameter asthe interior diameter of said envelope and being electrically insulatedfrom the exterior of said envelope.

7. A vacuum discharge tube comprising an envelope, electrodes mountedtherein and spaced to form a relatively long discharge-path for thedesired discharge between said electrodes, a plurality of electricallyconductive loop-like members within the envelope, said loop-like membersextending along said discharge-path and having substantially the sameexterior diameter as the interior diameter of said envelope and beingelectrically insulated from the exterior of said envelope; saidloop-like members together forming k a helically wound wire.

8. A vacuum discharge tube comprising an envelope having a tubularportion of insulating material, means providing an emissionalcathode atone end of said tubular portion, and means providing an anode at theother end of said tubular portion, said means comprising membersconstituting caps closing the respective ends of said tubular portion orthe envelope, a plurality of conductive, annular laminations within saidtubular portion and spaced along the inner wall thereof and electricallyinsulated from any external source of potential, said tubular portionbeing internally corrugated to provide means for mounting saidlaminations and to increase the length of insulating surface betweenadiacent laminations, the spacing between said laminations being suchthat, conforming with the corresponding distribution of the potential,the diiierence in potential between two adjacent laminations will besmaller than the minimum value necessitated by the vacuum to initiate asliding discharge between laminations.

9. A vacuum discharge tube comprising an envelope having a tubularportion of insulating material and end caps carrying respectively anemissional cathode and an anode, said cathode and anode being spacedapart to provide a relatively long discharge-path therebetween for thedesired discharge from cathode to anode, means electrically insulatedfrom any external source of potential comprising a plurality ofelectrically conductive loop-like members supported by the inner wall ofsaid tubular portion and extending along said entire discharge-pathacting when the potential difference to produce the desired dischargebetween cathode and anode is applied to the tube to divide the potentialdifierences along the walls of the tubular portion between adjacentportions of said loop-like members to such small values that the lengthof the paths along the walls of the tubular portion between suchadjacent portions of the loop-like members will be sufllcient to preventthe initiation of sliding discharges between said loop-like members.

10. A vacuum discharge tube comprising an envelope having a tubularportion of insulating material, the inner wall or said tubular portionbeing provided with closely spaced grooves providing annular projectionstherebetween, metallic end caps for said tubular portion carryingrespectively a cathode and an anode, and means for dividing thepotential diflerence along said inner wall comprising closely spacedannular laminations electrically insulated from any external source ofpotential, the spacing between said laminations being such thatconforming with the corresponding distribution of the potential, thedifierence in potential between two adjacent laminations will be smallerthan the minimum value necessitated by the vacuum to initiate a slidingdischarge between laminations, said grooves and projections constitutingmeans whereby said laminations are held in place on said inner wall andwhereby the length of insulating surface to prevent such slidingdischarges is increased.

ARNO BRASCH. FRITZ LANGE.

